Earlier quoted context omitted.
I’d go out on a limb here and conjecture that you can still by stuff from your own money without submitting a claim.
If the state requires it to be covered for all employees and it's subject to audit, whether or not I pay for anything additional, I'd still have to follow the policies and provide supporting documentation so my employer would be able to comply with the legal requirement. That's the hassle.
I fail to see the issue. These laws have good faith in them and of you refuse to give paperwork after multiple prompting you more or less waive that coverage. They have to follow the law but they can't force you to hand over your energy bill. Alternatively, they will estimate based on data they already have and throw it into soke benefits account (if one exists).
I also imagine there is a maximum coverage rate to prevent abuse, since existing laws require to pay only a portion based on how much office space you dedicate in your house.